i had the same thing happen to me a week or so ago, it was pretty intensely hot and humid one day and since then alot of them are dying and the survivors are all a gross yellowish tint rather than the clean white color they should be. I had about 4 of them that were still nice and white so I seperated them from the others to feed. I don't know if the bad looking ones are okay to feed, I'm not feeding them until they get healthy again (turn white again) , and if they don't , well then down the toilet they go